This invention is directed to novel processes for the recovery and at least partial purification of higher diamondoid components from hydrocarbonaceous feedstocks. Specifically, this invention is directed to recovery processes for obtaining compositions enhanced in one or more higher diamondoid components.
This invention is also directed to compositions comprising enriched levels of one or more higher diamondoids.
The following publications and patents are cited in this application as superscript numbers:                1 Fort, Jr., et al., Adamantane: Consequences of the Diamondoid Structure, Chem. Rev., :277-300 (1964)        2 Sandia National Laboratories (2000), World's First Diamond Micromachines Created at Sandia, Press Release, (Feb. 22, 2000) www.Sandia.gov.        3 Lin, et al., Natural Occurrence of Tetramantane (C22H28),Pentamantane (C26H32) and Hexamantane (C30H36) in a Deep Petroleum Reservoir, Fuel, (10):1512-1521 (1995)        4 Chen, et al., Isolation of High Purity Diamondoid Fractions and Components, U.S. Pat. No. 5,414,189, issued May 9, 1995        5 Alexander, et al., Removal of Diamondoid Compounds from Hydrocarbonaceous Fractions, U.S. Pat. No. 4,952,747, issued Aug. 28, 1990        6 Alexander, et al., Purification of Hydrocarbonaceous Fractions, U.S. Pat. No. 4,952,748, issued Aug. 28, 1990        7 Alexander, et al., Removal of Diamondoid Compounds from Hydrocarbonaceous Fractions, U.S. Pat. No. 4,952,749, issued Aug. 28, 1990        8 Alexander, et al., Purification of Hydrocarbonaceous Fractions, U.S. Pat. No. 4,982,049, issued Jan. 1, 1991        9 Swanson, Method for Diamondoid Extraction Using a Solvent System, U.S. Pat. No. 5,461,184, issued Oct. 24, 1995        10 Partridge, et al., Shape-Selective Process for Concentrating Diamondoid-Containing Hydrocarbon Solvents, U.S. Pat. No. 5,019,665, issued May 28, 1991        11 Dahl, et al., Diamondoid Hydrocarbons as Indicators of Natural Oil Cracking, Nature, 54-57 (1999).        12 McKervey, Synthetic Approaches to Large Diamondoid Hydrocarbons, Tetrahedron, :971-992 (1980).        13 Wu, et al., High Viscosity Index Lubricant Fluid, U.S. Pat. No. 5,306,851, issued Apr. 26, 1994.        14 Chung et al., Recent Development in High-Energy Density Liquid Fuels, Energy and Fuels, 641-649 (1999).        
All of the above publications and patents are herein incorporated by reference in their entirety to the same extent as if each individual publication or patent was specifically and individually indicated to be incorporated by reference in its entirety.
Diamondoids are cage-shaped hydrocarbon molecules possessing amazingly rigid structures that are superimposable fragments of the diamond crystal lattice1 (see FIG. 1). Adamantane, a ten-carbon molecule, is the smallest member of the diamondoid series, consisting of one diamond crystal subunit. Diamantane contains two face-fused diamond subunits, triamantane three, tetramantane four, and so on. While there is only one isomeric form of adamantane, diamantane and triamantane, there are four different isomeric tetramantanes; four different shapes containing four diamond subunits that can be superimposed on the diamond crystal lattice. Two of these isomers are enantiomeric (mirror images of each other). The number of possible isomers increases rapidly with each higher member of the diamondoid series. Because diamondoid crystal units can share more than a single face in some higher diamondoids, hydrogen to carbon ratios, i.e., the degree of condensation, also show increasing variation resulting in an increasing variety of molecular weights for each successive higher diamondoid family. FIG. 30 is a table depicting the range of higher diamondoids.
The parent diamondoids may be substituted with alkyls at various sites, and a myriad of methyl, ethyl, dimethyl, trimethyl, propyl, etc., substituted species are possible and occur naturally in petroleum feedstocks along with the parent diamondoids. Diamondoids are present in virtually every petroleum (oils and gas condensates) as well as oil source-rock extracts.11 The natural concentration of diamondoids in petroleum varies by orders of magnitude. For instance, methyldiamantane concentrations in relatively low-maturity crude oils from the central valley of California, are on the order of a few parts per million (ppm). Low-maturity oils sourced from the Jurassic-age Smackover Formation, Gulf Coast, USA, have methyldiamantane concentrations of 20-30 ppm. Deeply-buried petroleums such as gas condensate from deep formation, which have undergone substantial cracking as a result of intense heat, may have methyldiamantane concentration in the thousands of ppms.
The high diamondoid concentrations of some gas condensates and other feedstocks occur because of the high thermal stability of diamondoids compared to the other petroleum components. These diamondoids may be remnants of petroleum degradation by a geologic process over time and temperature conditions where other hydrocarbons were thermally cracked or reduced to gas and pyrobitumen. Because of this natural concentrating mechanism, in some gas condensates, diamondoids may become the dominant species. In addition, because they are extremely stable molecules, diamondoids survive and become concentrated in certain refinery streams after processing, e.g., cracking, hydrocracking, etc. The art has come to refer to adamantane, diamantane, triamantane and substituted analogs thereof as “lower diamondoids”. Tetramantane and larger diamondoids and substituted analogs are referred as “higher diamondoids”. That nomenclature is used herein. The lower diamondoid components show no isomers or chirality and are readily synthesized, distinguishing them from “higher diamondoids”.
Among other properties, diamondoids have by far the most thermodynamically stable structures of all possible hydrocarbons that possess their molecular formulas due to the fact that diamondoids have the same internal “crystalline lattice” structure as diamonds. It is well established that diamonds exhibit extremely high tensile strength, extremely low chemical reactivity, electrical resistivity greater than aluminum trioxide (Al2O3) and excellent thermal conductivity.
In addition, tetramantane and other higher diamondoids have sizes in the nanometer range and, in view of the properties noted above, the inventors contemplate that such compounds would have utility in micro- and molecular-electronics and nanotechnology applications. In particular, the rigidity, strength, stability, thermal conductivity, variety of structural forms and multiple attachment sites shown by these higher diamondoid molecules makes possible accurate construction of robust, durable, precision devices with nanometer dimensions. It has been estimated that MicroElectroMechanical Systems (MEMs) constructed out of diamond should last 10,000 times longer then current polysilicon MEMs, and diamond is chemically benign and would not promote allergic reactions in biomedical applications.2 The higher diamondoids would have similar attractive properties. Furthermore, some of the many isomers of the higher diamondoids possess chirality, offering opportunities for making nanotechnology objects of great structural specificity and ones which have useful optical properties. Applications of these higher diamondoids include molecular electronics, photonics, nanomechanical devices, and nanostructured polymers and other materials.
Notwithstanding the advantages of tetramantane and other higher diamondoids, the art fails to readily provide for compositions comprising these higher diamondoids.
For example, while Lin, et al.3 report the natural occurrence of tetramantane, pentamantane and hexamantane in deep petroleum reservoirs. However, they were only able to identify such compounds in ionized form as part of a mass spectroscopy analysis.
Likewise, while Chen, et al.4 discloses methods for isolation of high purity lower diamondoid fractions and components, the disclosed methods provide for distilling a diamondoid-comprising feedstock into 5 overhead components. These overhead components include unsubstituted adamantane, substituted adamantane, unsubstituted diamantane, substituted diamantane, and unsubstituted triamantane. Chen, et al. further recite that the pot material recovered after said distillation comprises a major amount of substituted triamantane and minor amounts of tetramantane and pentamantane. There was, however, no disclosure in Chen, et al. of the relative amounts of tetramantane and pentamantane in the pot material and Table 3 of Chen indicates only the presence of triamantane and tetramantane in the pot material and no attempt to isolare any high diamondoid is reported.
Other efforts to recover diamondoid fractions from naturally-occurring hydrocarbonaceous feedstocks have dealt with recovering the lower diamondoids illustrated by adamantane, diamantane and triamantane and various side-chain-containing analogues thereof primarily for the purpose of recovering these components from a natural gas stream in order to prevent operational problems in natural gas productions due to precipitation of these components in the production equipment. See, for example, the four related patents to Alexander, et al.5-8 One or more of these patents disclose: 1) extracting lower diamondoids from a gas stream with a solvent and further extraction by sorption on silica gel; 2) extracting lower diamondoids by use of a heat exchanger; 3) extracting lower diamondoids from a gas stream using a porous solid such as zeolite. Recovery of lower diamondoids from a gas stream is also disclosed by Swanson9 and recovery of lower diamondoids from a liquid stream is disclosed by Partridge, et al. 10
While synthetic routes to prepare diamondoids have provided for all of the lower diamondoids (adamantane through triamantane) by carbocation-mediated, thermo-dynamically controlled super-acid equilibration, this synthetic route, when applied to the synthesis of tetramantane and other higher diamondoids is blocked by severe kinetic (mechanistic) constraints. All attempts to synthesize the higher diamondoids by this thermodynamic equilibration route have proven futile. McKervey, et al.12 have reported, however, the synthesis in low yields (e.g.,˜10%) of anti-tetramantane from 1,6-dicarboxyl diamanatane using in the final step of the synthesis a gas-phase rearrangement over a platinum catalyst at 360° C. As is apparent, the use of such a starting material coupled with its low availability renders this synthetic procedure commercially unattractive and, moreover, it does not provide for the synthesis of other tetramantanes or other higher diamondoids.
In view of the above, there is an ongoing need in the art to provide for compositions comprising tetramantane and other higher diamondoids thereof. In view of the synthetic difficulties, there is also a need in the art to develop processes for recovering tetramantane and other higher diamondoids from natural sources.